chore(合并): 同步主分支变更并解决冲突

- 合并 wire/httpclient/http_upstream/proxy_probe 冲突并保留校验逻辑
- 引入 proxyutil 及测试，完善代理配置
- 更新 goreleaser/workflow 与前端细节调整

测试: go test ./...

backend/internal/handler/openai_gateway_handler.go

@@ -237,7 +237,7 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 				continue
 			}
 			// Error response already handled in Forward, just log
-			log.Printf("Forward request failed: %v", err)
+			log.Printf("Account %d: Forward request failed: %v", account.ID, err)
 			return
 		}